Casing with isolated annular space

ABSTRACT

The invention is comprised of (see FIG.  1 ) an inner pipe ( 2 ), and an outer pipe ( 3 ), and two end subs ( 1 ). An isolated circular hollowed space is contained in between these components. The isolated space can be used for transport of different medias down into the well, this can be vacuum, air, gas, acids, solids, tracers, or other well stimulating medias. The end subs ( 1 ) can be connected to the casing in the well and become an integrated part of the casing. The invention can be cemented on the outside like the casing can. The invention can be perforated after installed in the well.

The invention is related to a casing with isolated annular space. Theinvention can be applied in wells that are drilled for production ofhydrocarbons. The invention can be installed and used as an integratedpart of the casing that is penetrating a reservoir, or a zone in thewell that shall perforated.

Wells that are drilled in conjunction with production of hydrocarbonsare drilled in sections, starting with the biggest diameter at the top.Normally, a casing is installed in each section after the hole isdrilled. Each casing is normally cemented in place. The deepest sectionin the well will normally penetrate the zone of interest, which is thereservoir that will produce hydrocarbons, or the zone that it is plannedfor injection of water or gas. A casing will also normally be installedand cemented in place across the zone of interest.

Communication between the reservoir and the well bore is normallyobtained by the use of perforating guns. The perforating guns arenormally tubular loaded with many explosive charges that is shootingradial holes through the casing and cement and several feet into thereservoir rock. All charges are detonated at the same time. One of thechallenges related to the perforating technology is to remove theperforating debris from the perforating tunnels after the perforatingoperation. Debris left in tunnels will lead to excess fluid frictionduring production that could lead to lower production rate as a result.One effective method for cleaning the perforating tunnels to perforatein “under balance”. This is done by changing out the well bore fluidwith a low density fluid to lower the well bore pressure to a level thatis lower than the pressure in the reservoir prior to perforating. Thispressure differential between the reservoir and the well bore will leadto an immediately flow of fluid into the well when the casing isperforated. The result is a relatively high flow rate that will cleanthe perforating tunnels. There are methods available today for achievingsimilar cleaning effects without having to lower the well bore pressure.One method is to use atmospheric chambers in the perforating guns thatalso are perforated at the same time as the casing. The chambers willfill immediately due to the relatively high hydrostatic pressure. Thefilling of the atmospheric chambers will create an “under balance” inthe well that will give similar cleaning effect as obtained by changingout the well bore fluid.

This invention is based on using atmospheric chambers. The differencefrom the described methods is that chambers are an integrated part ofthe casing. The chambers are penetrated and punctured when perforatingthe casing. This is described in claim #1 in this application.

The invention is described in following figures;

FIG. 1 a shows a longitudinal cut of a preferable way of designing theinvention, consisting of an inner pipe (casing) and an outer pipe(casing) that is connected by two end subs.

FIG. 1 b shows a cut of a preferable way of designing the invention.

FIG. 2 a shows a longitudinal cut of an alternative way of designing theinvention, with support rings between inner pie and outer pipe.

FIG. 2 b shows a cut of an alternative way of designing the invention.

The invention consists of an inner pipe (1, 2), and an outer pipe (1,3), and two end subs (1, 1). In between these components there is anisolated, circular space that can be used for transport of differentmedia into the well, this can be vacuum, air, gas, different solids,acids, tracers, or other well stimulating medias. If the invention isexposed to high collapse forces during the installation, support rings(2, 4) can be installed. The end subs can be connected to the casing inthe well such as the invention becomes an integrated part of the casingAs the invention is a part of the casing, it can also be cemented inplace on the outside in the same way as for the casing.

One challenge in the perforating technology is to clean out perforatingdebris from the perforation tunnels. This invention can help clean outor stimulate the perforating tunnels immediately after the perforating.The perforating gun shoots from inside the invention, through theinvention, and out into the formation/reservoir that is on the outsideof the invention, leading to that the invention get punctured. If theisolated space is filled with air or gas that has a lower pressure thanthe formation, the space will immediately fill up with fluid from theformation. This immediately filling will give a washing effect in theperforating tunnels. If the isolated space is filled with an acid thatreacts with the reservoir rock or perforating debris, the acid couldflow into the perforating tunnels and give a stimulating effectimmediately after perforating if the pressure in the well bore is higherthan in the reservoir.

1. Casing with isolated annulus space characterised by that is comprisedof an inner pipe (2), and a outer pipe (3), two end subs (1), and inbetween these components an isolated, circular hollowed space that isused to transport different medium down into the well, the medium can bevacuum, air, gas, solids, fluids, tracers, or other well stimulatingmedias characterised by that the medias are released by perforating thecasing.
 2. Casing with isolated annulus space as described in claim 1,characterised by that it can be installed a an integrated part of thecasing in the well.
 3. Casing with isolated annulus space as describedin claim 1, characterised by that vacuum, air, or gas is transported inthe isolated space down into the well.
 4. Casing with isolated annulusspace as described in claim 1, characterised by that well stimulatingfluids are transported in the isolated space down into the well. 5.Casing with isolated annulus space as described in claim 1,characterised by that scale inhibitors are transported in the isolatedspace down into the well.
 6. Casing with isolated annulus space asdescribed in claim 1, characterised by that support rings (2, 4) areinstalled in the isolated space to avoid collapse due to pressuredifferentials.
 7. Casing with isolated annulus space as described inclaim 1, characterised by that a solid material that is transformed intogas when perforating is installed in the isolated space.